The overall objective of the proposed work is to define the effect of increases and decreases in renal sympathetic nerve impulse frequency on overall renal function. Studies involving both direct and reflex alteration in renal sympathetic nerve impulse frequency will be performed. Neuropharmacologically active compounds will be employed to further delineate these pathways. BIBLIOGRAPHIC REFERENCES: Ploth, D.W., Sawin, L.L. and DiBona, G.F.: Effect of Magnesium on Rat Nephron Sodium Reabsorption: A Segmental Analysis. Amer. J. Physiol. 230:398-402, 1976. Kaloyanides, G.J., Ahrens, R.E. Shepherd, J.A., and DiBona, G.F.: Inhibition of PGE2 Secretion Does Not Abolish Autoregulation in the Isolated Dog Kidney. Circ. Res. 38:67-73, 1976.